The US and Germany are building a state-of-the-art jumbo telescope on top of an airplane for advanced astronomical observations
Dr. Noah Brosh
It's called Sofia, but it's not the capital of Bulgaria, nor is it the name of a woman - but the name of the "Stratospheric observatory for infrared astronomy"
(Infrared Astronomy).
This research tool in the far infrared field, developed jointly by the USA and Germany, will be operational in 2003 and is planned to operate in space for about 20 years.
The Earth's atmosphere allows remote sensing of celestial bodies in a limited range of the spectrum. In the visible light region, the sky is more or less transparent - except for clouds, dust, and the scattering of a certain part of the light by the air molecules themselves.
In areas of higher energy - ultraviolet and x-rays, the atmosphere is opaque and observations that scientists want to make into the depths of space must be made by spacecraft.
Toward areas of lower energy than visible light - the infrared and millimeter radiation - various components of the atmosphere limit the observations. These are mainly molecules of substances in the atmosphere - water, carbon dioxide and more - that block the radiation reaching us from distant stars and galaxies.
To overcome all of this and open up these areas of the spectrum for research, it is necessary to raise a research instrument, such as a space telescope, above the high layers that contain the interfering molecules. They are mainly concentrated in the first few kilometers of the atmosphere layer above us.
One possibility to do this is using a space telescope - like the "Hubble" - but this task is very expensive and also limits the research telescopes to a relatively small diameter. The second option is to place a telescope in a high-altitude aircraft - fly. Such an aircraft operated for about twenty years. It was a military conversion of a "Boeing" 707 (KC 135), with an upper wing and carrying a telescope that was one meter in diameter. The plane flew to an altitude between 35 and 40 feet, for infrared observations. However, in 1996 NASA decided to take it out of service - and these days preparations are being completed for the operation of the next flying observatory, based on a larger plane - a modified version of a "Boeing" 747.
The US provides the project with the plane and makes the significant changes required, while a team of German scientists builds the telescope itself. As with the previous plane, the telescope will be viewed through a hole in the body of the plane. This requirement poses considerable challenges to the planners.
The main problem facing them: maintaining the stability of the telescope during the observation made while flying at such a high altitude. As all users of air transportation know, airplanes are not stable platforms like the rocks on which the ground telescopes are placed. The requirement facing the American and German planners is complete stability when the telescope image, due to oscillation, will be at the level of half an angle second.
In other words: you need a device that will make it possible to distinguish details the size of a one shekel coin, from a distance of four kilometers.
For this purpose, the telescope is separated from the fuselage and "floats" on liquid cushions. These correct the position of the telescope at every moment, to compensate for the "jumps" and vibrations of the plane's engine as well as other reasons.
The telescope itself, which is 2.7 meters in diameter, "peeks" out of the plane through a huge opening that remains open during the flight.
"Sofia" is a breakthrough in the field of airborne platforms for astronomical observations, but
It is not an aviation breakthrough. The plane and its many capabilities are based on military observation platforms that the USA developed to monitor missile launches by the USSR and other countries and also to investigate spacecraft in orbit around the Earth and, if necessary, to destroy them.
Happily, these military-war uses are now being applied to the advancement of science.
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